1. Field of the Invention
The present invention relates to an auxiliary instrument for fixing a rod, which connects bones such as thoracic vertebrae or lumbar vertebrae, in engaging grooves which each is formed on a head portion of an implant (a screw) screwed into the bone.
2. Description of the Related Art
In a conventional bone connector, as shown in FIGS. 1 and 2, a vertebral body 101 is integrally connected to an adjacent vertebral body 101 by screwing implants (screws) 103 into the vertebral bodies 101 and then fixing a rod 105 to head portions of the screws 103.
A work for fixing the rod 105 to each of the screws 103 will be described in detail below. Firstly, the rod 105 passes through an engaging groove 107 formed on the head portion of the screw 103. Secondly, a detent pin 111 is placed on an upper surface of the engaging groove 107. Finally, the detent pin 111 is screwed into the engaging groove 107 by means of a tool for rotating the detent pin 111. Here, a male thread portion and a female thread portion are formed on an outer surface of the detent pin 111 and an upper part of an inner surface of the engaging groove 107, respectively.
In the above fixing work, if the detent pin 111 wobbles, it becomes harder to screw the detent pin 111 into the engaging groove 107. Further, if the detent pin 111 is dropped from the engaging groove 107, it is possible to hurt an incision part of a patient.